The present invention relates to systems for separating a continuous strip of corrugated material into sections, and in particular to preparing the flat sheet material prior to corrugation to facilitate separation of the material into sections after it has been corrugated and/or during the corrugating process.
The use of corrugated structural material, particularly steel, has become quite popular relatively recently in two distinct applications. First, relatively thin gauge sheet material can be corrugated to provide the material with resistance to bending, and used as building panels in various construction applications. Second, a strip of flat sheet material can be corrugated and wound in a helical fashion to form corrugated pipe.
In the formation of corrugating building panels and in the formation of helically wound corrugated pipe, a roll of flat sheet stock is typically used. The flat sheet stock is fed from the roll into a corrugating machine, which forms the flat sheet stock into a continuous strip of corrugated material. In the formation of helically wound corrugated pipe, the strip of corrugated material is wound into the shape of the pipe and the edges are welded or mechanically locked together as with a Pittsburgh lock to form a continuous pipe. These procedures are quite streamlined and efficient, but unfortunately, the efficiency breaks down at the point when the strip of corrugated material is to be separated in the discrete building panels, or the continuous pipe is to be separated into discrete pipe sections.
When building panels are formed in the above described fashion, a continuous strip of corrugated material having a two dimensional profile emanates from the corrugating machine. It is desired that the two dimensional profile be quite deep, and that a substantial portion of the material be located at the extremities of the profile, using steep walls between the extremities, to maximize the bending resistance of the panels.
Shear blades are typically located downstream of the corrugating machine to separate the corrugated material into discrete building panels. For shallow profiles, corresponding shear blades with shallow corrugated edges provide an acceptable cutting tool. However, when the material is to be cut at an angle, such as to accommodate eaves, new shear blades must be provided with a different contour. Each time the contour of the materials change, or the cutting angle is changed, the shear blades must be changed as well. As a result, shearing the material becomes a complex and expensive process, and substantially increases the cost of the entire operation.
To shear building panels with shallow corrugated profiles, it is customary to provide shear blades in which one of the blades is inclined from horizontal so that the material is cut from one side to the other in a "scissors" fashion. However, this type of shearing interrupts the continuity of the forming process, which is a particular problem in high speed operations. Moreover, when panels are to be sheared which have deep profiles, and connecting sides at steep angles, it is necessary to use parallel shear blades which instantaneously shear the panel across its entire width. Unfortunately, instantaneous shearing of the entire panel requires massive equipment which is extremely expensive, especially when multiple sets of shear blades must be available.
An obvious solution to the above difficulties would be to cut the sheet stock into sections before it enters the corrugating machine (which requires long runout tables resulting in using more floor space). However, this is generally undesirable because it interrupts the forming operation and reduces the speed of the operation. Also, the quality of the corrugations is diminished at the ends of the corrugated segments because such ends are not restrained as they pass through the corrugating machine, as is the case when a continuous strip of sheet material is being corrugated.
Separating the helically wound continuous corrugated pipe into sections is even more complex. A saw is generally provided on a moving carriage where speed must be precisely matched with the speed of the pipe (see U.S. Pat. Nos. 3,198,043; 3,257,881; 3,369,432). Equipment for sawing the pipe is quite expensive, requires frequent maintenance, and is also noisy. The sawing operation forms an extremely sharp and dangerous edge on the pipe, and it is not uncommon for such pipe to be rejected because of its hazardous edges. The saw also forms burrs on the edge of the pipe, and an additional grinding step must be added, usually at the cost of much hand labor, to remove these burrs and the sharp edge from the end of the pipe.
In the manufacturing of small items, much smaller than the building panels and pipes discussed above, the technique of scoring the material prior to forming to facilitate subsequent sectioning is known. A rotating drum having a transverse knife edge is typically located upstream of the forming apparatus, and rotates so that its outer surface moves at the same speed as the material to be formed. When the knife edge contacts the material, it scores it perpendicular to its direction of travel, facilitating subsequent sectioning. However, this technique is not feasible with large pieces of sheet steel such as used in forming building panels and corrugated pipe because of the extremely large forces which would be generated when the knife edge struck the sheet material. Moreover, this technique cannot be adapted to helically wound pipe because the sheet stock must be cut at an angle, and this is difficult if not impossible with a rotating drum system.